Method of making heat exchange devices



Aug. 20, 1940. E. C. FRANCQFERREIRA 2,211,813

IIETHOD 0F MAKING HEKI EXCHANGE DEVICES Filed Nov. 19, 1938 2 Sheets-Sheet 2 mun Illlllll IIII 509A/wl C. Ffm/veo -FERRE/RA Patented Aug. 20,v 1940,

ME'rnon oF Mame. HEAT EXCHANGE nEvIcEs Edgard C. Franco-Ferreira, Chicago, Ill., assignor to Mich., acorporation Houdaille-Hershey Corporation,

Detroit, o! Michigan Application November 19, 1938, Serial'No. 241,305

- y 5 Claims. This invention relates to a heat exchange device and to a method oflmaklng the same. More par` the flow of the refrigerant. The continuous type l5 construction is relatively more expensive and the header type construction,vusing. headers formed of metal stampings, vis such as to present large areas that must be perfectly sealed if leaks are to be prevented.

It has also been proposd to dispense with headers and employ short U bends for joining the successive ends of straight lengths of tubing forming the body of the condenser, butEthis has the Y disadvantage of presenting a great number of 25 jointsl that mustv be perfectly sealed. The usual way of sealing such joints is by brazing or solder dipping, neither of which is entirely satisfactory as formerly practiced.. In the brazing operation, for instance, it has been customary to employ 30 copper orbrass brazing wires that must be inhalves, each comprising hairpin bends of tubing,

and the halves so formed are then united in a single brazing operation that also serves to bond the ns to the straight, parallel legs of said tub- 40 ing. The brazing operation is greatly simplified by rst plating the. hairpin bends of tubing with copper, which serves as the sole brazing agent in the operation. It is a comparatively simple matter, using the method of my invention, to obtain tight 45 joints betweenythe mated ends of the tubing and l bonds of high thermal vconductivity between the fins and the tubing. Also, my novel construction lends itself ladmirably to the manufacture of condensers of varying lengths, since with a minimum 50 Aamount of tooling, the tube length of the hairpin bend may be made longer or shorter, as desired,

to give a correspondingly longer or shorter length of condenser.

It is therefore an important object of this in-l (cl. zei-,1513) pensive method of. making heat exchangers, or condensers, which method eliminates the use of headers and reduces the number of joints that must be sealed to make the condenser uid tight.

It is a further important object of this invention to provide a method of making heat exchangers or condensers that lends itself peculiarly to the manufacture of large or small condensers with a minimum of tooling operations.

vIt is a further important object of this invention to provide a novel and improved construction of heat exchange devices, or condensers, that obviates the necessity of headers and that lends itself to more economical production.

Other and further important objects of this invention will be apparent from the disclosures i113 the specification and the accompanying drawgs. v

This invention trated .in the drawings and hereinafter more fully described.

n the drawings:

exchanger, or condenser, embodying the principles of my invention.

Figure 2 is a fragmentary view illustrating the method of manufacturing the condenser in two complementary halves.

Figure 3 is an end elevational view of the condenser of Fig. 1. Figure 4 is a sectional view taken substantially along the line IV-,IV of Fig. 1.

Figure 5 is a fragmentary, broken, enlarged plan view of the condenser.

Figure 6 is an enlarged sectional view taken substantially along the line VI-VI of Fig. 5.'

Figure Z is an enlarged fragmentary, detail view of themating Aend of the tubing prior to assembly.

As shown on the drawings: In Figs. 1, 3 and 4, the reference numeral I Il indicates generallya heat exchange device or con- -denser embodying the principles of my. invention. Said condenser in its finished form comprises lengths of tubing II, on the straight, parallel legs I2 ofv which are mounted transverselyextending .ns I3. Said fins I3 may suitably Vbe provided with longitudinally extending,r` corrugations III, which serve to increase the heat radiating surface of the fins. In the preferred embodiment of my invention, both the tubing II and ns I3 are formed of plain carbon or soft steel. End plates I5 and Inpreferably of dead soft steel, lie outside of the fins I3 and just inside the U.bends of the tubing.

In the manufacture of the condenser III, steel (in a preferred form) is illus- Figure 1 is a broken top plan view of a heat tubing is rst bent into U- or hairpin tubes, such as the tubes I 1 and I8 (Fig. 2) with straight, parallel legs I9 and 20, respectively, of the desired length. The legs I 9 of the tubes I1 are then flared at their ends 2|, as best shown in Fig. 7, to constitute the female members, and the corresponding ends of the legs 20 of the tubes I8 are reduced, as at 22, for insertion into the flared ends 2l. The tubes I'I and I8 are then provided for their full lengths, or for the straight lengths thereof, with a coating of brazing material, represented by the layer 23 (Fig. 7), which may suitably be a copper electroplat'e. The thickness of copper plate is preferably a minimum of about 0.0006 inch, but may be more or less `as required. Instead of copper plating the YL I-bends, a layer of copper, brass or other brazing material may be adherently applied as in powder or paste form to the tubing, or only to the swaged ends thereof..

After the tubes have been copper plated, or otherwise provided with brazing material on their outer surfaces, the end plates I5 and I6 and the ns I3 are mounted in position upon the straight lengths I9 and 20 of the respective tubes I1 and I8. The mounting of the ns and end plates on the straight lengths of the tubes Il. and I8 may be performed before forming the tubes with mating ends, and, as is obvious, must be performed in advance of flaring the ends of the tubes I9. The end plates I5 and I6 and the ns I3 are all provided with annual collars, similar to the collar 24 (Fig. 5) surrounding the tube receiving apertures and the collars and apertures are of such a diameter as to provide a close t for the legs of the tubing. There are thus formed two complementary halves, represented by the reference letters A and B (Fig. 2) and constituting the tubes I'I and associated end plates I5 and fins I3, and the tubes I8 and associated end plates I6 and ns I3, respectively.

The complimentary halves A and B are next joined by forcing the respective ends I9 and 22 of the tubing into a telescopic t, each reduced end 22 being force tted into the corresponding flared end 2| until said flared ends 2I rest inabutting relationship against the shoulders 240 of the reduced ends 22 (Fig. 6)

The assembled condenser unit I0 is next subjected to a brazing operation, which may suitably comprise passing the unit into a furnace having a non-oxidizing, or reducing atmosphere heated to a sufficiently high temperature to melt the copper of the electroplate layer 23 and cause the copper to now into around the joints between the mating ends 2l and 22 of the tubing and between the annual collars 24 of the ns and the outside of the tubing. In general, a temperature of between 1850 and 2000 F. is satisfactory for effecting the brazing of the parts together. Higher or lower temperatures, however, may be used depending upon the metal of which the condenser is made and the composition of the brazing material. In a reducing atmosphere, such as an atmosphere relatively rich in hydrogen, the brazing material flows readily by Virtue of capillary action into the close fitting joints, and upon the cooling of the condenser unit after leaving the furnace, the joints will be found to be uid tight and of high thermal conductivity.

As shown in Fig. 1, the condenser I0 may be provided with two or more ends for connection in a refrigerant system, such as the ends 25 and 26 at theextremities of the tubing, and the ends 2'I and 28 intermediate the extremities of the unit. These ends 25 to 28 inclusive are closed by means of caps 29 immediately subsequent to the con pletion of the condenser units, in order to prevent rusting of the insides of the tubing or the introduction of foreign material into the tubing. These caps 29 are not removed until the condenser unit is actually put into a refrigeration installation.

It will be evident from the foregoing description that the use of relatively long lengths of tubing to provide hairpin or U-bends for the complementary half sections of the condenser eliminates all joints in the fluid conduits other than the joints along the median line of the condenser when the half sections are united. In accordance with this invention, these joints are of the press nt, telescoping type, so that when brazed, they can readily be made uid tight. By merely selecting the length of tubing originally necessary to give the desired overall length of condenser, any size of condenser can be made YVWith a minimum amount of tooling.

The use of copper plating, as above described, obviates the use of any other form of brazing material, the copper of the electroplate constituting the sole brazing means for all of the joints of the condenser. This results in considerable saving in manual labor over the application of brazing wire, shims or the like, as has heretofore been customary.

I am aware that many changes may be made and numerous details of construction may be varied through a Wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention:

1. The method of making a heat exchange device, which comprises forming U -shaped bends of tubing having straight parallel legs open at their ends, reducing the ends of some of said tubes, expanding the ends of others of said tubes to telescopingly receive said reduced ends, copper plating said tubing, assembling fins on said legs to form complementary half sections, press fitting said reduced and expanded ends of said half sections together and heating the assembled unit to a brazing temperature to cause said copper plating to melt and serve by itself to bond said halves together and said fins to said tubing legs.

2. The method of making a heat exchange device, which comprises forming a plurality of sets of U-shaped tubing with mating ends, plating said tubing With brazing material, assembling fins on the legs of said tubing to form complementary halves, mating the ends of one half with the ends of the other half to provide a continuous conduit through a plurality of turns of said tubing and heating the assembled unit to a sufficiently high temperature to effect brazing of said mated ends together and of said fins to said tubes through the flow of said brazing material. l

3. The method of making a heat exchange device, which comprises forming a plurality of sets of steel U-shaped tubing with telescoping ends, plating said tubing with brazing material, assembling steel ns on the legs of said tubing to form complementary halves, press fitting to telescope the ends of one half with the ends of the other half to provide a continuous conduit through a plurality of turns of said tubing and heating the assembled unit to a sufficiently high temperature to effect brazing of said mated ends together and of said fins to said tubes through the ow of said brazing material as the sole bonding medium.

fifi

am Leia 4. The method of making a heat exchanger which comprises bending tubing into U-shape to provide a plurality of U-shaped members eachv having a pair of spaced legs, coating the tubing with brazing material, assembling lns on the legs of the tube members to provide complementary heat exchanger sections, forming mating male and female ends on the legs of the U-shaped members in the complementary sections, press tting the mating ends of the legs into telescoping relation, and heating the assembled units to a sumcie'ntly high temperature to elect brazing together of the telescoped members and of said ns to said members through the iiow of the brazing material coating.

5. The method of making a heat exchanger from tubes, apertured end plates, and apertured ns which comprises providing a coating of bonding material on the tubes, bending the tubes into U shape to form a plurality of conduit members each having spaced parallel legs, inserting the legs of the members through the apertures of the end plates and iins to position the members in the plates with each end plate disposed adjacent the U-bend of a member and bridging the space between the legs thereof and to position the fins in spaced transverse relation on the members for forming complementary heat exchanger sections, forming press-fit ends on the legs of the complementary sections, press-fitting said ends together to provide a continuous passage through a plurality of turns of the tubes, and heating the assembled unit to a sufficiently high temperature to eiect a bonding together of the press-tted -leg ends as Well as a uniting of the iins and end plates to thetubes through ow of the bonding material coating on the tubes.

EDGARD C.l FRANCO-FERREIRA. 

